Coastal Construction Manual - National Ready Mixed Concrete ...

4 SITING
Figure 4‐19.
As buildings in this
Humbolt County,
CA, community are
threatened by bluff
erosion along the
Pacific Ocean, they are
moved to other sites on
the jointly owned parcel
In extreme cases, entire communities have been threatened by erosion and have elected to relocate. For
example, the village of Shishmaref, AK, voted in November 1998 to relocate their community of 600 after
storm erosion threatened several houses and after previous shore protection efforts failed.
More information on specific examples of relocation of threatened buildings can be found in FEMA 257,
Mitigation of Flood and Erosion Damage to Residential Buildings in Coastal Areas (FEMA 1994). The report
also presents several examples of flood and erosion mitigation through other measures (e.g., elevation,
foundation alterations).
4.5.3 Lot Configurations near Tidal Inlets, Bay Entrances, and River Mouths
Layout of lots and infrastructure along shorelines near
tidal inlets, bay entrances, and river mouths is especially
problematic. The three South Carolina houses in Figure
4-20 were built between January 1995 and January 1996,
approximately 2 years before the photograph was taken in
July 1997. They were built 100 or more feet landward of the
vegetation line, but rapid erosion associated with a nearby tidal
inlet left the houses standing on the beach only two years after
construction. The shoreline will probably return to its former
location, taking several years to do so. Although the buildings
are structurally intact, their siting can be considered a failure.
CROSS REFERENCE
Section 3.5 also describes
instances where the subdivision
and development of oceanfront
parcels near ocean-bay
connections led to buildings
being threatened by inlet-caused
erosion.
Figure 4-21 shows condominiums built adjacent to the shore in Havre de Grace, MD, where the mouth of
the Susquehanna River meets the head of the Chesapeake Bay. Although the buildings are elevated, they
are subject to storm surge and flood-borne debris. Infrastructure development and lot layout in similar
cases should be preceded by a detailed study of historical shoreline changes, including development of (at
least) a conceptual model of shoreline changes. Potential future shoreline positions should be projected, and
development should be sited sufficiently landward of any areas of persistent or cyclic shoreline erosion.
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